Narrator (April Hobart, CXC): The word galaxy comes from the Greek word meaning "milky circle" or the more familiar Milky Way.
The white band of light across the night sky that we call the Milky Way was poetically described long before Galileo, but with his small telescope, what he discovered was a multitude of individual stars, so numerous as almost to surpass belief.
Today we know that the Milky Way is our home galaxy, a vast rotating spiral of gas, dust and hundreds of billions of stars.
The sun and its planetary system formed in the outer reaches of the Milky Way about 4.5 billion years ago.
See the Milky Way through Chandra's eyes.